An aircraft turbine engine generally includes a core having, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. One or more shafts may be provided to drivingly connect the turbine section to the compressor section, and optionally, to drivingly connect the turbine section to a load. When such an aircraft engine is incorporated into a rotary aircraft, such as a helicopter, the one or more shafts of the aircraft engine may be mechanically coupled to a main rotor of the rotary aircraft such that the main rotor may provide lift for the rotary aircraft.
Given the nature of air travel, it is generally desirable to ensure the aircraft engine is operating properly before and/or during flight, and to maintain or overhaul such aircraft engines before the aircraft engine degrades past a certain threshold. One measure of degradation of an aircraft engine is an engine torque factor of the engine. The engine torque factor refers to a ratio of a current maximum corrected torque available to a maximum corrected torque available to a nominal engine (e.g., of a typical new engine). When the engine torque factor drops below a certain threshold, it may be determined that the engine needs to be taken “off wing” and maintained or overhauled.
One way for determining an engine torque factor is by utilizing one or more baseline engine power models providing a correlation of a corrected engine temperature to corrected engine torque. The baseline engine power models are typically developed based on a nominal aircraft engine for the various stages of the nominal engine's degradation. However, it is not uncommon for a degradation of an aircraft engine to vary from that of the nominal engine (i.e., to degrade more quickly or more slowly). Accordingly, as the above described method for determining a particular engine's engine torque factor does not take into consideration how the particular engine is actually operating, the engine torque factor thresholds for determining when an engine should be taken off wing to be maintained and/or overhauled can be overly conservative. This may result in prematurely taking an aircraft engine off wing and unnecessary maintaining/overhauling such engine.
Therefore, a method for determining an engine torque factor specific to the particular aircraft engine would be useful. Further, a method for determining an engine torque factor capable of taking into consideration certain operating conditions and/or ambient conditions of the aircraft engine would be particularly beneficial.